Vodacom Huge Incorrect Data Charges

I called Vodacom on 14-APR to know WHY my portable WiFi is NOT connecting and I got an ans from call center \That my data is depleted on 2-APR around 12 PM and it's softlocked bcoz 4GB data is downloaded"I never use this in my office as I have free WiFi at office and 2-APR is Thursday"